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Occupational Injuries and Infections

General conlrol is a difficutt problem. Whcrc infection is suspccted in dcad birds it is rec-ommended to wet the feathers with dis-infcctant.

Q Fcvcr (query fever)

In the 1966 study of Scottish abattoir workers 28.1% had antibodies to phnse 2 antigen of Co.riclla burnctii, the cause of Q fever. A survey in 1953 showed a 2.13% incidencc in the generał population. In 1966 in Northern Ireland 28.3% of abattoir workers were positive and 24-4% of^yetennariąns^ although there hąd been no evidence of O fever in animals or humans 10 years previously.

Q fever was first officially recognized in the United Kingdom in 1949 and is now routincly tested for in the differential diagnosis of cascs of pneumonia and pyrexia of unknown origin in man. Between 1975 and 1980 an average of 100 cases annually were reported to the Public Health Laboratory Service in England and Wales. Outbreaks are rare, but often the source of infection is difficult to establish. Cat-tle and sheep are usually considered to be the main rescrvoirs of infection.

In recent years in Australia Q fever has been such a serious cause of illness among abattoir workers that vaccination of susceptible per-sonriel was tried. 924 non-immune volunteers were inoculated with a Coxiclla burnctii phase 1 vaccine and while 34 cases of Q fever occurred in 1349 unvaccinated workers, nonę occurred in the vaccinated subjects in the fol-lowing 18 months.

The disease in man^s an_aęuje iehrile.dis-ease with sudden onset, mąlaisę,.anorexia and weaknesśTasting for 1-2 weeks. Pneumonia is present and the mortality ratę is Iow. Death is most often due to endocarditis, and the severity of the disease inereases with age. Infections without symptoms arc somctimes observed.

In some countries the disease is officially classified as occupational. It is transmitted by the biłeś of ticks and by the inhalation of infected dust, but rarely by the ingestion of contaminaled meał and milk. C. burnctii rcmains infective in wool, cotton and farm dust for very long periods. The disease in farm animals occurs most often in ruminants, especially goats, sheep and cattle, but many wild animals as we!! as farm stock may act as reservoirs.

C. burnctii can multiply in the gcnit.nl traci and mammary gland of cattlc, sheep and goats, and apparently healthy stock are known to shod large numbers of the organisni in milk, urinc, faeccs and especially the placenta and feta! fluids. Thcse animals appear to be able to harbour the infection without ill-effects although cases of bronchopneumonia and abortion due to Q fever havc * been occasionally recorded.

Ringworm (tinea capitis, kerion, favus)

Ringworm is a disease caused by a closcly related group of fungi known as__der

ma tophytes_and may occur in workers hand-ling and slaughtering cattle dugng the winter— when animals are normally affected (Platę I,

Fig 2).

Diagnosis is best carried out by the rpirro-scopic, examination of affected _hairs when fungal hyphae and arthrospores will be scen after the hairs havc been treated with 20-30% potassium hydroxide.

As with contagious pustular dermatitis, infection is most commonly by direct contact with infected animals but may also occur through indirect contact. Since ringworm spores can exist on animals' skins without causing any lesions, such animals may be important sources of infection. As for many human skin affections injuries in the form of cuts, abrasions and maceration of the super-ficial skin layers are probably predisposing factors (Fig. 12.2).

The common forms of ringworm in cattle are Trięhophyton yerrucosum and less commonly T. mentagrophytes.

Streptococcal meningitis

A disease of pigs caused by Streptococcns su i 5 typc 2 and characterized by meningitis has been recognized in the United Kingdom and the Netherlands sińce 1973. Recent survcys have shown that the disease is widespread in pigs in the United Kingdom, especially in the south and east^

Since the first outbrcak in 1973 there was an inereasing number of new outbreaks recorded to a peak in 1976 after which there was an apparent decline but this may havc been due to veterinary surgeons diagnosing the disease without rccourse to veterinary inves-